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- TRI -STATE GENERATION AND TRANSMISSION ASSOCIATION, INC. <br />HEADQUARTERS: P.O. BOX 33695 DENVER, COLORADO 80233 -0695 303 - 452 -6111 <br />September 19, 2014 <br />Mr. Rob Zuber Jcr c J Lu'N <br />Environmental Protection Specialist <br />Colorado Division of Reclamation, Mining & Safety DIMSiONOF RECLAMATM <br />Department of Natural Resources MINING AND SAFETY <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />RE:. Colowyo Coal Company L.P., Mine Permit C -1981 -019, Technical Revision 'So. 104 <br />(TR -104), East Taylor Ditch Modification <br />Dear Mr. Zuber: <br />Tri -State Generation and Transmission Association Inc. (Tri- State), is the parent <br />company to Axial Basin Coal Company, which is the general partner to Colowyo Coal Company <br />L.P. (Colowyo). Therefore, Tri -State on behalf of Colowyo is submitting three (3) copies of TR- <br />104 to Permit C- 1981 -019. <br />Colowyo has made a determination that the long -term stability of the lower section of the <br />riprap channel in the East Taylor Ditch would be enhanced if peak flow was reduced through the <br />addition of up to a two acre -foot inline ditch impoundment structure at the transition point, from <br />the vegetated channel to the lower riprap channel located near Station 20 +00. The proposed <br />location of the inline impoundment is identified on Exhibit 7 -14I. Figure 1. This figure also <br />includes pertinent hydrologic drainage boundary assumptions and curve numbers given a worst <br />case hydrologic condition and reclamation scenario at year 2018. <br />The SEDCAD model runs for both conditions have been included. The specific design of <br />the impoundment will conform to the general limitations and guidelines identified within Figure <br />2.05 -6 Stock "Tank Plan/Profile Typical Design. <br />SEDCAD allows the user to output tabular flow data at any point in the model network. <br />Colowyo extracted data from both SEDCAD models. Exhibit 7 -14I. Figure 2 is a graphical <br />demonstration of the peak flow through the downstream riprap channel with and without the <br />proposed impoundment. As the figure illustrates, the peak flow rate of the downstream channel <br />below the pond is reduced from 49 cfs to 17 cfs. <br />Also included with this package are a revision application, a change of index sheet to <br />ease incorporation into the permit document, and a copy of the public notice for your review. <br />4N F00AL ORPORTUN1TN AFFiRt IATIt F -1k, I SON � t ✓iP! .? r r'Fi <br />A T uch,louu' Enrr,,%-Z'ooper,lrive <br />CRAIG STATION ESCALANTE STATION NUCLA STATION <br />PO. BOX 1307 P.O. BOX 577 PO. BOX 698 <br />CRAIG, CO 81626 -1307 PREWITT, NM 87045 NUCLA, CO 81424 -0698 <br />970 -824 -4411 505- 972 -5200 970 - 864 -7316 <br />